1. Field of the Invention
This invention relates to vehicles having sprung rigid axles.
2. Description of the Prior Art
In a vehicle having a rigid axle which is conventionally sprung using leaf springs, the characteristics of the spring-restoring force in bump and in roll are usually dissimilar. By "bump" we mean that both ends of the axle are deflected during travel of the vehicle through substantially the same distance perpendicular to a reference plane of the body or chassis of the vehicle and by "roll" we mean that one end of the axle is deflected relative to the other in directions perpendicular to said reference plane. When the vehicle stands on a horizontal surface the reference plane will be horizontal. Thus for a given deflection of the axle relative to the reference plane in bump the spring-restoring force will be greater than that if one end of the axle should be deflected by the same distance i.e. in roll. This is because it is not normally practicable to arrange the springs over the wheel centres. If, for example, leaf springs are arranged halfway between the axle centre and the wheel centres, the spring-restoring force will only be one-quarter in roll of that which it is in bump, assuming the same deflection of the wheel or wheels. This is because in roll the springs deflection will only be one-half of that of the deflected wheel and the restoring moment arm will also only be one-half of what it would be were the springs arranged over the wheel centres.
Moreover, the axial displacement of the spring-restoring force and the wheels induces large bending moments in the axle which has to be of massive construction to withstand these moments.
It is an object of the present invention to provide a vehicle having a sprung axle which may be arranged to give substantially equal spring-restoring forces in bump and roll.